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Abstract:

The present invention overcomes image defects such as the brightness
inclination or smears by reducing the line resistance of a power source
bus line which supplies electricity to organic EL elements. A plurality
of pixels which are arranged in a matrix array is connected to power
source lines, and the plurality of power source lines are connected to a
power source bus line. Both ends of the power source bus line are
connected to a power source part via a FPC. By supplying electricity to
both ends of the power source bus line from the power source part, the
line resistance of the power source bus line can be reduced.

Claims:

1. An organic EL display device comprising: a substrate having a display
region; a flexible printed circuit connected to the substrate; and a
drive circuit disposed on the substrate, wherein: the display region
includes a plurality of pixels arranged in a matrix array, power source
lines connected to the plurality of pixels, and data lines supplying data
signals to the plurality of pixels, a power source bus line extends along
a side of the display region and is connected to the power source lines,
the power source bus line is arranged between the display region and the
drive circuit, electric power is supplied from a power source part via
the flexible printed circuit to a plurality of portions of the power
source bus line, and a cathode contact is connected to cathodes of the
plurality of pixels, and cathode electrons are supplied from between an
edge of the substrate and the power source bus line via the cathode
contact.

2. An organic EL display device according to claim 1, wherein the cathode
contact is arranged opposite the power source bus line from the display
region.

3. An organic EL display device according to claim 1, wherein the cathode
contact is arranged between the power source bus line and the drive
circuit.

4. An organic EL display device according to claim 1, wherein the cathode
electrons are supplied to the cathode contact via the flexible printed
circuit.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a Continuation of U.S. application Ser. No.
11/710,944 filed on Feb. 27, 2007. Priority is claimed based on U.S.
application Ser. No. 11/710,944 filed on Feb. 27, 2007, which claims
priority from Japanese application JP 2006-051235 filed on Feb. 27, 2006,
which is hereby incorporated by reference into this application.

Background

[0002] 1. Field of the Invention

[0003] The present invention relates to an organic EL display device which
uses organic EL elements as pixels, and more particularly to an improved
power source wiring which supplies electricity for allowing the organic
EL elements to emit light.

[0004] 2. Description of the Related Art

[0005] An organic EL element is a current-light-emitting-type element
which emits light when an electric current flows therethrough, wherein a
large current of several tens to 100 mA flows in a power source line in
the inside of a TFT substrate on which the organic EL elements are
formed. Particularly, in performing fixed-voltage driving of an EL
display panel, when electricity is supplied to respective pixels via the
power source line in the inside of the TFT substrate from a terminal at
an inlet of the display panel, due to a voltage drop which is generated
attributed to the resistance of the power source line, image defects such
as the brightness inclination, smears and the like are generated.
Accordingly, it is necessary to reduce the resistance of the power source
line in the inside of the TFT substrate (from the inlet of the display
panel to the respective pixels).

[0006] With respect to the reduction of the power source resistance, in
following patent document 1, there is described a technique in which, for
lowering a voltage drop attributed to the resistance of a drive power
source line which drives a plurality of organic EL elements arranged in a
matrix array, auxiliary power source lines are connected to both ends
(and an intermediate portion) of a drive power source line.

[0007] Patent document 1: JP-A-2003-108068

SUMMARY

[0008] In the above-mentioned patent document 1, although the voltage drop
of the drive power source line which is connected to a plurality of
organic EL elements is lowered, a voltage drop of the auxiliary power
source lines which are connected to the plurality of drive power source
lines is not taken into consideration.

[0009] Accordingly, it is an object of the present invention to provide an
organic EL display device which reduces a voltage drop of a power source
bus line which supplies electricity to a power source line which is
connected to a plurality of organic EL elements.

[0010] The present invention is directed to an organic EL display device
which includes a power source line which is connected to a plurality of
organic EL elements and a power source bus line which is connected to the
power source line, wherein electricity is supplied to a plurality of
portions including both ends of the power source bus line or both ends of
the power source bus line.

[0011] According to the present invention, it is possible to obtain the
organic EL display device which can reduce the voltage drop attributed to
the line resistance of the power source bus line which supplies
electricity to the power source line of the organic EL elements thus
effectively overcoming image defects such as the brightness inclination,
smears or the like attributed to the power source bus line.

[0012] The display device according to the present invention is applicable
to a TV receiver set, a PC monitor, a notebook type PC, a PDA, a mobile
phone, a digital still camera, a digital video camera, a car navigation
monitor and the like. Further, the display device according to the
present invention is also applicable to other self-luminous
light-emitting-type display.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 is a general appearance view of an organic EL display device
according to the present invention;

[0014] FIG. 2 is a drive circuit diagram of the organic EL display device
of an embodiment 1 shown in FIG. 1;

[0015]FIG. 3 is a detailed view of a pixel made of an organic EL element
shown in FIG. 2;

[0016] FIG. 4 is a drive circuit diagram of an organic EL display device
of the second embodiment;

[0017] FIG. 5 is a drive circuit diagram of an organic EL display device
of the third embodiment;

[0018]FIG. 6 is a drive circuit diagram of an organic EL display device
of the fourth embodiment;

[0019] FIG. 7 is a drive circuit diagram of an organic EL display device
of the fifth embodiment;

[0020]FIG. 8 is a drive circuit diagram of an organic EL display device
of the sixth embodiment; and

[0021]FIG. 9 is a drive circuit diagram of an organic EL display device
of the seventh embodiment.

DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, the present invention is explained in conjunction with
embodiments by reference to drawings.

Embodiment 1

[0023] FIG. 1A and FIG. 1B are general appearance views of an organic EL
display device according to the present invention, wherein FIG. 1A is a
front view and FIG. 1B is a cross-sectional view. In FIG. 1A and FIG. 1B,
a pixel part 12 is formed on a TFT substrate (display panel) 11, and the
pixel part 12 is sealed by the TFT substrate 11, a sealing substrate 13
which faces the TFT substrate 11, and a sealing material 14. In a sealed
space, for preventing the degradation of organic EL elements in the pixel
part 12 attributed to moisture, a desiccant material 15 is sealed.
Further, on the TFT substrate 11, a FPC (Flexible Printed Circuit) 16 for
supplying signal for driving the organic EL elements and for supplying
electricity from a power source part is mounted.

[0024] FIG. 2 is a drive circuit diagram of the organic EL display device
shown in FIG. 1. In FIG. 2, pixels 22 each of which is formed of the
organic EL element are arranged in a matrix array in a display region 21.
The plurality of pixels 22 are connected to power source lines 23 and the
plurality of power source lines 23 are connected to a power source bus
line 24. Both ends of the power source bus line 24 are connected to a
power source part 25 via the FPC 16. In this manner, the organic EL
elements in the pixels 22 emit light with the electricity supplied to
both ends of the power source bus line 24 from the power source part 25.

[0025] Further, the plurality of pixels 22 which are arranged in a matrix
array are connected to scanning lines 26 and data lines 27, and are
driven in response to scanning signals of the scanning lines 26 selected
by a scanning line drive circuit 28 and data signals from the data lines
27 which are connected to a data line drive circuit 29.

[0026] A display control part 30 receives signals from the outside and
supplies the scanning signals and the data signals to the scanning line
drive circuit 28 and the data line drive circuit 29 via the FPC 16 and,
at the same time, controls the power source part 25. Although the power
source part 25 and the display control part 30 are mounted on the FPC 16
in the drawing, it is not always necessary to mount the power source part
25 and the display control part 30 on the FPC 16.

[0027] Here, a cathode contact 31 is connected to cathodes of the organic
EL elements in the pixels 22, wherein the cathode contact 31 is grounded
to the TFT substrate 11 and, at the same time, is grounded to the FPC 16
via the FPC 16.

[0028]FIG. 3 is a detailed view of the pixels 22 each of which is
constituted of the organic EL element shown in FIG. 2. In FIG. 3, in each
one of the plurality of pixels 22 arranged in the inside of the display
region 21, a switching TFT 41 which is selected by the scanning line
drive circuit 28 and acquires the data signals from the data line drive
circuit 29, a capacitance 42 which stores the data signals, and a driver
TFT 44 which drives the organic EL element 43 in response to the data
signals are provided. The power source part 25 is connected to both ends
of the power source bus line 24.

[0029] The organic EL element 43 has an anode side thereof connected to
the driver TFT 44 and a cathode side thereof connected to a cathode
current line 45 which holds a reference potential (ground potential), and
the cathode current line 45 is connected to the cathode contact 31.

[0030] In this embodiment, electricity is supplied from both ends of the
power source bus line 24 and hence, compared to the supply of electricity
from one terminal, it is possible to lower a voltage drop attributed to
the line resistance of the power source bus line 24. By lowering the
voltage drop in this manner, it is possible to reduce the brightness
inclination in the horizontal direction of the horizontal power source
bus line 24. Here, the brightness inclination in the vertical direction
attributed to the voltage drop of the vertical power source line 23 is
ignored.

Embodiment 2

[0031] FIG. 4 is a drive circuit diagram of an organic EL display device
of an embodiment 2 corresponding to FIG. 2 of the embodiment 1. The
constitution which makes this embodiment differ from the embodiment 1
lies in that electricity is supplied to a plurality of portions including
both ends of the power source bus line 24. Since other constitutions are
substantially equal to the corresponding constitutions shown in FIG. 2,
the detailed explanation is omitted.

[0032] In FIG. 4, electricity is supplied to the plurality of portions
(five portions) including both ends of the power source bus line 24 from
a power source part 25 on the FPC 16 side. By supplying electricity to
the plurality of portions in this manner, the line resistance of the
power source bus line 24 is divided thus achieving the substantial
reduction of line resistance.

[0033] In this embodiment, compared to the embodiment 1, a voltage drop
attributed to the line resistance of the power source bus line 24 can be
further lowered thus further reducing the brightness inclination.

Embodiment 3

[0034] FIG. 5 is a drive circuit diagram of an organic EL display device
of an embodiment 3 corresponding to FIG. 2 of the embodiment 1. The
constitution which makes this embodiment differ from the embodiment 1
lies in that a drive circuit includes an upper power source bus line 51
and left and right power source bus lines 52, 53. Since other
constitutions are substantially equal to the corresponding constitutions
shown in FIG. 2, the detailed explanation is omitted.

[0035] In FIG. 5, one ends of a plurality of power source lines 23 are
connected to a lower power source bus line 24, and another ends of the
plurality of power source lines 23 are connected to the upper power
source bus line 51. Further, the lower power source bus line 24 and the
upper power source bus line 51 are connected with the left power source
bus line 52. Further, the right power source bus line 53 may be connected
to the lower power source bus line 24 and the upper power source bus line
51 so as to surround the display region 21 with these power source bus
lines.

[0036] Electricity is supplied to both ends of the power source bus line
24 from a power source part 25 on the FPC 16 side and, at the same time,
electricity is also supplied to the upper power source bus line 51 via
the left power source bus line 52 (and the right power source bus line
53). By supplying electricity from both ends of the power source line 23
in this manner, it is possible to lower a voltage drop of the power
source line 23.

[0037] In this embodiment, along with the lowering of the voltage drop of
the power source bus line 24, the voltage drop of the power source line
23 can be lowered and hence, the brightness inclination in the horizontal
direction can be reduced in the same manner as the embodiment 1 and,
further, the brightness inclination in the vertical direction attributed
to the line resistance of the power source line 23 can be also reduced.

Embodiment 4

[0038]FIG. 6 is a drive circuit diagram of an organic EL display device
of an embodiment 4 corresponding to FIG. 4 of the embodiment 2. The
constitution which makes this embodiment differ from the embodiment 2
lies in, in the same manner as FIG. 5 of the embodiment 3, that a drive
circuit includes an upper power source bus line 51 and left and right
power source bus lines 52, 53. Since other constitutions are
substantially equal to the corresponding constitutions shown in FIG. 4,
the detailed explanation is omitted.

[0039] In FIG. 6, electricity is supplied to a plurality of portions (five
portions) including both ends of the power source bus line 24 from a
power source part 25 on the FPC 16 side and, at the same time,
electricity is also supplied to the upper power source bus line 51 via
the left power source bus line 52 (and the right power source bus line
53). By supplying electricity to both ends of the power source line 23
from the power source bus line 24 and the upper power source bus line 51,
a voltage drop of the power source line 23 is lowered.

[0040] In this embodiment, along with the further lowering of the voltage
drop of the power source bus line 24, the voltage drop of the power
source line 23 can be also lowered and hence, the brightness inclination
in the horizontal direction can be further reduced in the same manner as
the embodiment 2, the brightness inclination in the vertical direction
attributed to the line resistance of the power source line 23 can be also
reduced.

Embodiment5

[0041] FIG. 7 is a drive circuit diagram of an organic EL display device
of an embodiment 5 corresponding to FIG. 5 showing the embodiment 3. The
constitution which makes this embodiment differ from the embodiment 3
lies in that a drive circuit includes an upper FPC 71 which supplies
electricity from both ends of the upper power source bus line 51. Since
other constitutions are substantially equal to the corresponding
constitutions shown in FIG. 5, the detailed explanation is omitted.

[0042] In FIG. 7, a power source part substantially equal to a power
source part 25 on a lower FPC 16 side is provided to an upper FPC 71
side, and electricity is supplied to both ends of the upper power source
bus line 51 from this power source part on the upper FPC 71 side. The
line resistance of the upper power source bus line 51 is reduced in the
same manner as a lower power source bus line 24. Here, a left power
source bus line 52 and a right power source bus line 53 which connect the
upper power source bus line 51 and the lower power source bus line 24 may
be omitted.

[0043] In this embodiment, compared to the embodiment 3, the brightness
inclination in the horizontal direction can be further reduced.

Embodiment 6

[0044]FIG. 8 is a drive circuit diagram of an organic EL display device
of an embodiment 6 corresponding to FIG. 6 showing the embodiment 4. The
constitution which makes this embodiment differ from the embodiment 4
lies in that a drive circuit includes an upper FPC 71 which supplies
electricity to a plurality of portions including both ends of an upper
power source bus line 51. Since other constitutions are substantially
equal to the corresponding constitutions shown in FIG. 6, the detailed
explanation is omitted.

[0045] In FIG. 8, a power source part substantially equal to a power
source part 25 on a lower FPC 16 side is provided to an upper FPC 71
side, and electricity is supplied to a plurality of portions (five
portions) including both ends of the upper power source bus line 51 from
this power source part on the upper FPC 71 side. The line resistance of
the upper power source bus line 51 is reduced in the same manner as a
lower power source bus line 24.

[0046] In this embodiment, compared to the embodiment 4, the brightness
inclination in the horizontal direction can be further reduced.

Embodiment 7

[0047]FIG. 9 is a drive circuit diagram of an organic EL display device
of an embodiment 7 corresponding to FIG. 8 showing the embodiment 6. The
constitution which makes this embodiment differ from the embodiment 6
lies in that left and right power source bus lines 52, 53 are provided
with left and right FPCs 72, 73. Since other constitutions are
substantially equal to the corresponding constitutions shown in FIG. 8,
the detailed explanation is omitted.

[0048] In FIG. 9, a power source part substantially equal to a power
source part 25 on a lower FPC 16 side is provided to an upper FPC 71 and
a left FPC 72 (and a right FPC 73), and electricity is supplied to a
plurality of portions (five portions) including both ends of an upper
power source bus line 51 and a left power source bus line 52 (and a right
power source bus line 53) from these power source parts. The line
resistances of these upper power source bus line 51 and left power source
bus line 52 (and right power source bus line 53) are reduced in the same
manner as a lower power source bus line 24.

[0049] In this embodiment, the line resistances of the upper, lower, left
and right power source bus lines can be reduced and hence, the brightness
inclination attributed to the power source bus lines can be reduced to
extremely small values.